This survey presents the practical application of immunohistochemistry additional to clinical anamnesis and histology (HE staining) in the differential diagnosis of morphologically similar lesions. First of all, the algorithmic approach for immunohistological diagnosis of undifferentiated or non-classifiable malignant neoplasias of the female genital tract is described and the significance of immunohistochemistry for the differential diagnostic discrimination and the histogenesis of organ-specific gynaecological neoplasias is re-assessed.